The ESP Guitar Company

Necessary, no; however it wouldn't technically be a bad idea so if you have the means to do so, I'd recommend it.

i did just as a precautionary measure, but no, not necessary since the EMGs are shielded internally..

also if you're doing an install, no need to connect a bridge ground wire due to the same reason, internal shielding... if you do, i dare you to put your mouth on a mic and play your guitar while plugged up!